A new study shows that a bacterium that causes appendicitis and gum disease is also found in colon tumors. Researchers suggest that it may set the stage for colorectal cancer, the second-deadliest malignancy.
The bacterium – fusobacterium might play a role in determining the prognosis of colorectal cancers and shaping their treatment, according to two research teams independently reporting a relationship between the rod-shaped microbe and cancers of the lower digestive system.
Fuscobacterium is known to lead to inflammation, gum disease and appendicitis. Scientists have tied some strains to two inflammatory bowel diseases, ulcerative colitis and Crohn's disease, both of which elevate the risk of colon cancer. They noted that the bacterium is sticky, which helps explain its presence in the dental plaque that clings to tooth enamel.
A Canadian research team found significantly more fuscobacterium RNA (a type of genetic material) in colon tumors than in healthy tissues from the same people. That surprised the investigators because fuscobacterium is a rare inhabitant of healthy guts and “has not been previously associated with cancer,” said Robert Holt, a senior scientist with the British Columbia Cancer Agency Genome Sciences Center and associate professor at Simon Fraser University in Vancouver.
Simultaneously a U.S. group compared tissues lining cancerous and healthy regions of patients' colons, looking in each for stretches of the microbes' DNA (another type of genetic material). Looking first at tissues of nine people, and then 95 more, they found a spike in fuscobacterium species, especially fuscobacterium nucleatum, fuscobacterium mortiferum and fuscobacterium necrophorum in diseased tissue.
“Tumors and their surroundings contain complex mixtures of cancer cells, normal cells, and a variety of microorganisms such as bacteria and viruses,” said Dr. Matthew Meyerson, co-director of the Center for Cancer Genome Discovery at the Dana-Farber Cancer Center in Boston and senior author of the second study. “Over the past decade, there has been an increasing focus on the relationship between cancer cells and their 'microenvironment,' specifically on the cell-to-cell interactions that may promote cancer formation and growth.”
Both studies are published online Tuesday in the international journal Genomic Research.
Meyerson said additional studies comparing bacteria in the tissues of cancer patients and healthy people could demonstrate whether there are more fuscobacterium species in the intestines of colon cancer patients than in the intestines of the general population. Researchers are embarking on comparison studies of Fusobacterium levels in larger numbers of patients with colorectal cancer and in those without the disease. Also planned are studies to determine whether the bacterium can be used to induce colon cancer in animal models.
The American Cancer Society estimates that colon cancer will cause more than 49,000 deaths in the U.S. this year, and more than 141,000 people will be diagnosed with the disease.